A remarkable study for "Flaming June," one of the best known of all Pre-Raphaelite paintings, has been discovered hanging discreetly behind a bedroom door in an English country mansion.

The discovery of the head study for Sir Frederic Leighton’s picture was announced on Friday – one of many extraordinary secrets to emerge from a 16th-century manor house owned by Mary, Duchess of Roxburghe until her death, aged 99, last year.